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Solar Drive
"YO-HO and Blow the Man down! I tell you Karl, nothing like trimming the sails on a out system-run like this that makes me want to sing and drink rum and dance on a sea-chest." "Keep singing and I'll keel-haul you without the benefit of a suit..." ~Drew Vorchet and Karl Takamura, SSS Calliope, Stellar Cruise Line ---- How it works Solar Sails, Also referred to as Light sails or Photon sails, are in essence a form of propulsion that uses the Radiation pressure from a system's primary (Called "Solar wind") to interact with a reflective thin material that uses the impact to provide thrust. Similar in operation to how regular sails on a planet will capture the impact of wind as a motive force, propelling a craft across land or sea. The difference is the material and size required. All spacecraft within a system are affected by Solar Radiation pressure, which accounts for needs for minor course corrections or projective calculations on a ballistic course to take such into consideration. This method of propulsion uses that pressure, spread out over a wide area, with less mass to provide motive force. Consisting of a Central Module for the craft, and a nearly separate sail, usually connected by way of a central hardpoint and numerous tethers that can be tightened or loosened to adjust the angle of intercepting vector, the spacecraft are fairly distinguishable by the several standard kilometer sized sail. Some sails are equipped to serve as both motive force and provide primary energy (Through solar heat and photonic absorption exchange) for the ship, effectively freeing up a great deal of the ship itself for carrying beings and cargo. Though the sheer effective size of the craft in relation to it's "drive" (the sail) is comparatively much much smaller, if disproportionate in mass. (For most advanced societies the sail tends to weigh much less than the ship itself, it's just this mass is spread out over a wider area.) Solar Sails work anywhere in a planetary system or even in interstellar space, however they become more effective at providing acceleration the closer they are to a primary, and thus see a great deal more use in a inner solar system than outer. ---- Variations Beam Sailers are a variety of Drive that instead of relying entirely on solar radiation pressure for thrust, makes use of energy beams projected at the sail itself. usually from a stationary orbital array, or sometimes from the rear of the craft itself (though in the latter case it's mostly either using the sails for Aesthetic reasons, or the additional thrust to assist with steering or "tacking" on a course that takes one inwards towards the primary instead of away). Beam sailers gain the ability to go at speeds faster in the outer planetary ranges, or go against the prevalent pressure from the primary, however they do require a nearly constant focused burst of the energy from whatever is providing it, and if going against the "current" more energy is needed to both drive the ship and overcome the pressure from such a course. Electro-magnetic sails are a variation on the sail design which instead of using a large reflective material (that can suffer from tearing or impact damage) uses a great lattice-work that creates an electro-magnetic field all through itself. This harnesses the radiation pressure as it presses against the EM field, and can sometimes allow for larger sails with the same mass as smaller solid ones because of the space between the latticework. The ship will need a separate reactor, however, for this as generating a strong enough EM field requires some power. Vector Shield Sails are some of the most advanced types, as they rely on one-way vector shielding and no physical sail at all. The projectors create and manipulate the vectored shield which in some cases may be entirely invisible (though distortion effects of the actual pressure may cause a "shimmer" similar to an atmospheric "glow"). The shields themselves make up no mass, and thus effectively allow for better thrust conversion, they do require a generator to provide the field which oftentimes requires it's own power source. ---- Benefits and Drawbacks. A great many beings like the aesthetics of a Solar-sail type craft. Xeno-psychologists tend to believe it has to do with inherited memories of some of the planetary use of craft similarly, and a fascination with objects that are shiny. The fact that, like the ramscoop drive, the fuel source for the ship is constantly all around you and thus doesn't need to be stored on board and thus saves space that otherwise would be handed over to engines for thrust is another benefit. Systems with intense primaries or more than one Primary oftentimes make great use of solar sailers for shipping, working and even pleasure craft. It's already been hinted at that the large sails are prone to damage. The Thin materials can be damaged by meteors or other fast moving particulate matter, or may even tear under stress as they are adjusted. Acceleration is another difficulty, as it takes a while for the pressure to build and thus provide the needed acceleration. Additionally making adjustments to the sometimes kilometer long sails can take a slow time over the course of hours before it's properly aligned, so high maneuverability is also hampered. For beam-sailers the energy use and needing to be directly on target as the craft moves away can cause all manner of difficulties. if the transmission array is off by half a degree at it's base, this could cause a shift on the sail where one part is receiving more pressure than the other and shift the course of the ship or cause stress damage depending on the type of energy used. ---- So is it or is it not? The Universe is wide and diverse, and thus all over will you see various ships of various types, some with deployed "sails" some without, in all manner of Configurations. Not all of them are using a solar drive, though they look quite similar. Some deployed sails are used for collecting energy from the primary to re-charge the ship's core and power it's systems, where it uses an entirely different form of drive for actual maneuvering. Other make use of a similar design to gather interstellar gasses and particles to convert as fuel similar to a collapsible ramscoop. And in these cases some will use the sail to gather particulate matter ahead and behind in such a way as to use in a linear accelerator similar to a ramscoop drive. And still others may have a function that is technical, however mostly deploy the sails while moving for the sheer aesthetic look of a tall ship with it's glowing energy sails billowing in the solar wind, while their gravimetric drive brings them in to dock.